Tube cleaner



Dec. 17, 1935. v.15. BAKER 2,025,009

TUBE CLEANER Filed Oct. 28, 1933 2 Sheebs-Sheet l mum V. H. BAKER TUBECLEANER Dec. 17, 1935 Filed Oct. 28, 1935 2 Sheets-Sheet 2 Patented Dec.17, 1935 UNiTED STATES PATENT OFFICE Lagonda Manufacturing Company,

Springfield,

Ohio, a corporation of Ohio Application October 23, 1933, Serial No.695,639

9 Claims. (01. 15-10413) The invention pertains to mechanical tube andpipe cleaners of the gyratory type and more particularly to a sectionalcutter head comprising separable units and an improved method ofmounting the cutter elements therein.

The present tube cleaner is capable of a wide range of industrialapplications not only in heat exchange apparatus but in other tube andpipe installations. Due to chemical reaction and precipitation of solidmatter entrained in flowing liquids, the tubes of boilers, stills,condensers and evaporators become encrusted with scale and deposit ofextreme hardness which clogs such passages, reducing their capacitiesand thermally insulating the walls. Water and other pipes are likewisesubject to corrosion and deposits of solid matter which retards flow andincreases pump resistance.

The present device is adapted to remove such objectionable deposits bymechanical action wherein the scale and encrustation is disintegratedand dislodged by the cutting and abrading action of hardened rotarycutting elements carried in a rotary head in such manner that theyprogressively attack the deposits and automatically accommodatethemselves to changing contour and size of the encrusted interior of thetube and to deflections and curvatures thereof.

The present cutter head comprises in advance roughing cutter unitwherein cutter elements are mounted in converging relation for rotationabout fixed axes and a finishing cutter unit wherein the cutters aremounted on floating axes for automatic adjustment under centrifugalinfluence to compensate for the progressive enlargement of the bore ofthe tube due to removal of deposit. These units are usable conjointly orsingly as may be required by the character and extent of the deposit tobe removed. The axes of the floating cutters of the finishing unit whenin position of adjustment are inclined to the axis of rotation of thehead but not in the same plane, thereby giving to the head a slightlyhelical characteristic affording a screw effect by which automaticfeeding action is achieved. The longitudinally inclined cutters of theroughing unit, also preferably though not necessarily, are set in aslightly askew relation with the axis of the head. Such inclination ofthe cutters of either unit is ordinarily approximately but two degreesout of axial alignment but obviously may be more or less, according toconditions of operation. The mounting trunnions of such cutters areprovided with peripheral enlargements of polygonal form,

. which their axial displacement is prevented without interference withtheir radial shifting motion, and enabling the use of trunnions ofmaximum hardness without being subject to undue breakage.

The object of the invention is to simplify the 5 I construction as wellas the means and mode of operation of gyratory tube cleaners wherebythey may not only be economically manufactured, but will be moreefiicient in use, automatic in operation, of increased durability,easily operated and 10 unlikely to get out of repair. a

A further object of the invention is to provide a cutter head of markedsimplicity, having but few parts, and those parts of relatively largesize, With no small parts to be easily lost, and capable l5 of easy andfool-proof assembly.

A further and important object of the invention is to provide a deviceof great flexibility and applicable to widely varying operatingconditions by forming the device which may be used as a 20 single entityfor unison operation or part of which may be used independently of theremainder, as the character of the work may necessitate.

A further object of the invention is to provide an improved form ofcutter pin or trunnion shaft 25 and to enable the retention of themaximum strength of the trunnion shafts for the cutters by providingperipheral enlargements which not only serve as bearings but have thrustengagement to prevent axial displacement of such trun- 3 nions andobviate the necessity of reducing the sections of the shafts byflattening and thereby weakening them.

A further object of the invention is to dispose the cutters in suchrelation as to minimize resistance toadvance movement and induce anautomatic feeding action.

A further but none the less important feature of the invention is toprovide for changing the inclination of the cutter pin or trunnionrelative 40 to the carrying head to vary or reverse the feeding action.

A further object of the invention is to provide an improved floatingmounting for planetary cutter elements enabling their automaticadjustment into effective relation with the work.

A further object of the invention is to increase the period ofusefulness of the cutter trunnions, by enabling them to be presented insuccessive positions of rotative adjustment whereby the wear thereon maybe uniformly distributed.

A further object of the invention is to provide a cutter head for a tubecleaner having the herein mentioned desirable characteristics.

With the above primary and other incidental 50 rinacvertical tube.

tapered: pilot portions and body portions of'larger objects in view, aswill more fully appear in the specification, the invention consists ofthe features of construction, the parts and combinations thereof, andthe mode of operation, or their equivalents, as hereinafter describedand set forth in the claims.

In the drawings wherein is shown the preferred, but obviously notnecessarily the only form of embodiment of the inenvtion, Fig. 1 is aperspective view of the assembled cutter head. Fig. 2

is a side elevation showing the roughing and finishing units separatedfrom each other. is a longitudinal sectional view. Fig. 4 is atransverse sectional view. Fig. 5 is a detail perspective view of one ofthe cutter trunnion shafts.

Fig. 6 is a detail View of the structure shown in Figs. 1 to 4 andillustrates a fragmentary end view of Fig. 8. Fig. 7 is a detail view ofan abutment plate. Fig. 8 is a diagrammatic plan view of Fig. 6illustrating the relative adjustments of the cutter'pin to a quiteexaggerated degree. Figs. 9 and l0'show a finishing cutter and aroughing cutter-respectively as used alone. Fig. 11 is a diagrammaticView illustrating the angularity of i;.thea-cutters.. Fig; 12 is asectional view taken substantially on line |2-l2 of Fig. 3.

Like parts are'indicated by similar characters ofwreference throughoutthe several views.

Rotary cutter heads for removing scale and aovfiother deposits fromtubes and pipes are quite old in the art. Such devices are progressivelyadvanced through. a clogged or encrusted pipe or tube-and. are rotatedby a suitable air or steam motor either directly connected and following."..the cutter head throughthe tube or stationarily mounted outside thetube and operativelyconnected with the advancing cutter headwby anextendible drive shaft. The scale, or coke, to bearemoved from theinterior of tubes and pipes 40 :varies: greatly in character, degree ofhardness andcidepth of deposit. Many times a relativelythin-depositofegg-shell character is found to be extremely hard. Such thin depositbeing beyond ,the range of operation of the roughing the finishing andburnishing unit alone is efdiameter provided with floating cutters havebeen heretofore used such heads have been of inseparable or unitarycharacter, heavy and cum- El-berSome,-and unadaptable to universal use,and

the cutter trunnions. have usually been laterally notched or flattenedto fit their mounting, and hence 'materially' weakened, necessitatingtrunnion shafts of-relativelylarge diameter; By proflvidinggseparablecutter headunits, forming the subjectamatten hereof, one designed forheavy or roughing service and the other for finishing and smoothing orburnishing action, which; may beconnected with the actuating motorindepend- :ently'of the roughing cutter with which it may be alsointerconnected for unison operation, the deviceis given universalcharacter and made applicable'to a much wider variety of work, andfurther when the burnishing or finishing unit Jalone. is used less poweris required for operation. Whereas the flattening of the cuttertrunnions heretofore for engagement in the mountingx'materially weakenedthe shaft or pin resulting in excessive breakage, the polygonal enilargement of the. trunnion shafts at. their points Fig. 3

of engagement with the mounting materially strengthens these pins andserves duo-functionally to aiford non-rotative sliding lateralengagement of the trunnion shaft with its mounting in any one of severalpositions of. rotative adjustment, and to limit the shafts against axialdisplacement without the necessity of auxiliary detachable fasteningdevices. By disposing the axes of the cylindrical bodies of the pinslightly eccentric or off center relative to the polygonal enlargements,the relation of the axes of the pins or trunnion shafts to the axis ofrotation of the head may be changed to different inclinations and indifferent planes or aligned with the axis of the head to thereby varythe self-feeding effect, or neutralizing such tendency as conditionsdictate as will appear more fully later. It is desirable when operatingin Vertical tubes to reverse the inclination of the cutters so that theywill possess a tendency to feed backward, and thus to some extent opposegravity influence and counteract the weight of the suspended cutterhead, driving motor and supply hose, which together are relativelyheavy.

The roughing. cutter unit A includes a spoollike rotary carrier ormounting comprising a core or shaft I laterally concaved or grooved at|-a to accommodate the roughing cutters and having. a relatively smallintegral head 2 at the end. The opposite end of the core is formed witha polygonal shoulder 3 to receive a removeable disc'or head 4 of greaterdiameter, having a polygonaltcentral opening fitting the shoulder 3, andwhich abuts against a collar 5 on the core or shaft portion I receivablewithin a recessed;

seat in the face of such disc or head l.

The respective heads 2 and 4 of the mounting are provided with taperedbearing seats 6to receive the trunnions of a series of planetaryroughing cutters .l which are carried by the mounting in convergingrelation to each other and inclined to the axis of rotation. The bearingseats 6 for the cutter trunnions on one head are preferably though notnecessarily slightly offset in the direction of rotation relative to thebearing seats intheother head whereby the roughing cutters 1 areslightly inclined relative to the direction of rotationof the head B butnot in the plane, thereof. This rotative inclination is ordinarily buttwo or three degrees from a position normal to theplane of rotation, butobviously may be varied according to different conditions of operationand variations of the character of the=cleposit to be removed. If I8 isso positioned, that is the center position disclosed in Fig. 6, as tohave the cutter axially aligned with the axis of the carrier if one ofthe pins does wear it might be rotated through one hundred eightydegrees so as to present the other side of the pin for wear to beequalized. Now let it be assumed that the'cutter is positioned so thepin is offset to the right as disclosed in Fig. 6 and let it be assumedthat the carrier rot-ates in a counterclockwise direction. The pinwears. It is found desirable to equalize the wear by rotating member l9through one hundred eighty degrees and re verse the direction ofrotation of the carrier so as to cause itto rotate in a clockwisedirection. The wear is equalized. This may be clearly seen by referringto the disclosure shown in Figs. 6, S and schematically in Fig. 11.

At its rear end the core or shaft portion of the mounting extends beyondthe removable head 4 and is screw threaded for detachable engagementrelatively spaced heads IB and II integrally interconnected by convexwall portions forming a substantially cylindrical hollow body havingflat ends and provided with peripheral openings to receive the cutterelements. The rear head II] is provided with radial rectangular slots I2intersecting the periphery of the head and a central polygonal hub I3 toreceive a complementary removable abutment plate M having a centralpolygonal orifice to receive the hub I3 and also provided with radiallyelongated holes or slots I5 registering with the open end slots I2 ofthe head Ii) when the plate I4 is in position. The opposite head II ofthe mounting cage is provided with radially elongated holes or slots I6corresponding with the slots I5 of the abutment plate I4.

Located within the peripheral openings or pockets of the carrier areindependently revoluble cutter elements I! and I'|-a which may be ofvarious shapes or sizes and of different surface configuration. Thoseshown for illustrative purpose comprise cylindrical serrated cuttersI'I-a. and fluted conical cutters I'I assembled in pairs. These cutters,whether multiple or single, are mounted for floating motion radiallyunder centrifugal influence within the limits of the slots I5 and I6,and are of such length as to conform rather loosely to the spaceintermediate the heads III and I I between which they are confined. Thegyratory flinishing and burnishing cutters I1 and I'll are mounted ontrunnion shafts or cutter pins I8 for rotation about their own axessimultaneously with their rotation about the axis of the cutter head.Heretofore it has been the practice to flatten the trunnion shafts orcutter pins on one or both sides for engagement in the mounting head.For longevity and effective service it is quite desirable that thesecutter pins be hardened. The indentation of the sides of the pins asheretofore practiced materially weakened the structure and there hasbeen frequent breakage at such points.

Contrary to such-former practice, instead of reducing the pins or shaftsat their points of engagement with the mounting, the pins are materiallyenlarged .and strengthened at such points.

In the present instance the cutter pins I8 are provided with polygonalenlargements I9 which slidingly engage in the radial slots I2 of themounting for bodily movement of the trunnion pins and cutters mountedthereon in radial directions under centrifugal influence. Theseperipheral enlargements I9 are duo-functional and not only materiallyincrease the strength of the pins at their points of engagement with thecarrier and provide improved sliding bearing surfaces thereon, but theyalso provide thrust bearings or abutment shoulders to limit the axialdisplacement of the pins. The polygonal form of the pin bearings enablesthe pins to be reengaged from time to time in different positions ofrotative adjustment to equalize the wear thereon and increase theirperiod of usefulness. Being of increased section at their bearing pointsat which breakage has heretofore usually occurred the cylindrical bodiesof the pins may be of less diam eter without sacrificing strength. Thecutter elements I1 and I'Ia, or such other types of cutters as may besubstituted therefor, are assembled on the pins, and the smaller ends ofthe pins are projected into the slots or elongated holes I6 in the headII, while the polygonal enlargements l9 engage within the radial slotsI2 of the head II).

In such relation the forward ends of the cutters having clearance topermit axial movement may abut upon the inner face of the head II of thecarrier, .and the shoulders afforded at the forward sides of thepolygonal enlargements I9 may abut upon the rear ends of the cutters tolimit the axial movement of the cutter in one direction. The pins I8 areprovided with reduced terminals 20 beyond the peripheral enlargementsI9, which extend within the radial slots I6 of the abutment plate I4, tolimit the radial movement of the pin with respect to the axis ofrotation of the cutter head. The cutter .pins or trunnion shafts I8 andwith them the cutters I! and I'I-a mounted thereon are free for radialfloating motion within the limits of the slots I5 and I6, while the pinsare held against rotary motion by the engagement of their polygonalenlargements I9 within the slots I2, and at the same time are heldagainst axial displacement by the abutment of the same peripheralenlargements in one direction upon the ends of the cutters and in theopposite direction upon the complementary abutment plate I4.

The pin receiving slots of the respective heads I and I I of the rotarycarrier or mounting may be longitudinally aligned with each other butare preferably slightly offset in the direction of rotation of the headwhereby the axes of the respective cutter pins are disposed slightlyaskew or inclined relative to the direction of rotation. Suchinclination is usually approximately two degrees, but may be more orless to meet particular conditions of use.

In the event that such pins having eccentric bearing enlargements aredisposed in longitudinally aligned slots I2, I and I6, by adjusting thepins through partial rotative movements the relation of the pins to therotative carrier may be materially altered. By disposing the pins in theslots I2 with the direction of eccentricity lying in a plane of the axisof rotation of the head or aligned with the slot, the pin is positionedcloser to or farther from the axis of rotation, but in longitudinalalignment with the carrier. By a quarter turn of the pin by which thedirection of eccentricity of the body and enlargement of the pin istransverse to the radius of the carrier one end of the pin will bedeflected laterally independently of the other end of the pin out oflongitudinally aligned relation with the mounting into an askew orinclined relation relative to the axis of rotation of the head but notin a plane of the axis of rotation. By turning it in one direction forengagement in the slot I2, it is inclined in one direction and by givingthe pin a half turn in reverse direction for reengagement in the slot I2it is inclined in a contrary direction.

By inclining the axes of the cutters with respect to the axis ofrotation of the head but out of the plane of said axis the device isgiven a screwlike effect which affords an automatic feeding action.Referring to Fig. 11, the axis of the revoluble cutter elements I! and1m may coincide with the dot-dash line I8a and the axis of the cutter 1along the line Ia so as to have ascrew-like effect to automatically feedthe cutters. If desirable the angle of inclination may be reversed fromIaw to I81; and from Ia to 1b so as to reverse the direction of thescrew thread-like effect, thereby effecting a backward rather than aforward action or vice versa. Instead of reversing both axes, only onemay be reversed so that the 75 1 direction of inclination of thecutters.

screwxthread-like effect of one cutter is in part at least counteractedby the screwthread effect of the other. This automotive action may beeffected forwardly or backwardly according to the The latter is quitedesirable at times when the cutter head is suspended in asubstantially'vertical tube or pipe in which case the tendency to feedreversely assists in supporting the apparatus and relieves 'theweight'sustained by the operator. The hub of the head I I of the carrieror mounting is provided with a screw threaded opening for reception ofthe threaded end ill of a coupling member 22 by which the cutter headmay be attached to .a

driving motor, or for reception of a threaded end ofa drive shaftconnected to a remote power device.

The inclination of the axes of the cutters to thedirection of rotationof the carrier as used in the specification and claims may be defined ashaving the axes of the cutters intersecting all planes common to theaxis of the carrier.

The roughing cutter unit A and the finishing cutter unit B are usableconjointly, or the roughing cutter may be detached and the finishingunit B alone utilized. This is the customary practice in using thedevice disclosed. However, if so desired the screw threaded extremity ofthe roughing cutter may be employed to interconnect the roughing cutterunit directly with the drivin'g power independently of the finishingunit. Thus the combination cutter head is universal in character andcapable of a wide range of applications. The improved form of mountingpin obviates the problem of breakage, enables the pins to be adjusted tocompensate for wear and by employing eccentrically disposed bearingportions upon the pins the latter are capable of further. angularadjustment and also to different spaced relation with the axis of thehead. While for illustrative purpose the angularity of the cutter pin [8has been greatly exaggerated in Fig. 8 it isto be understood that thisangularity will ordinarily be approximately two or three degrees andthat to accommodate such angular adjustment the slots l2 and i6 may bemade with sufficient clearance or sloppy fit ,which in any event wouldbe quite small. The conical roughing cutters 'i-l being mounted oninclined fixed axes in the forward unit A are unyielding when forciblythrust intooperative engagement with the coke. deposit or encrustationwithin a tube and have effective and positive engagement therewithinsuring enlargement of the bore suflicientlyto permit free passage ofthe larger rear unit B. andthe driving motor If yieldingly mounted or.of flexible character such assembly would tend to collapse or contractunder the resistance of the coke deposit and consequently -the rear unitB and driving motor could not follow, into the passage defined by suchcollapsed roughing unit or would be in danger of becoming wedged thereinor would resist rotation due to tightness of their fit. The unyieldingrelation of the roughing cutters rotating on their fixed axes definingan orbital path siightly larger at all times than the diameter of theburnishing cutter carrier and the motor facilitates uniform operationunder pressure or force feed conditions when operating upon heavy cokedeposits of hard character. The integral trunnions 8 of tlole roughingcutters i being tapered and engaging in correspondingly tapered seats inthe respective mounting. heads 2 and 4 not only provide increasedstrength, but facilitate the assembly of axial movement of the removablehead 4 in a.

direction angular to the fixed axes of the respective cutters, which!would not be possible if these trunnions were straight. The taper of thetrunnions is upon a degree substantially equal to the convergentangularity of the axes of the cutters, thus disposing the outer sides ofthe bearing seats in the head 4 and the inner sides of the'seats in thehead 2 substantially parallel with each other and parallel with the axisof the carrier, whereby the several trunnions are simultaneouslyengageable in their bearing seats by a straight relative movement of thecutters and heads parallel with the axis of the cutter head.

To protect the bearing seats of the tapered trunnions 8 againstexcessive thrust pressure, the

larger ends of the inclined tapered cutters I are chamfered and havethrust engagement against the head 4 outside such bearings, thuslimiting the longitudinal play of the cutters and relieving thetrunnions and their bearings.

From the above description it will be apparent to the specific featuresshown, but that the means and construction herein disclosed comprise thepreferred form of several modes of putting the invention into effect,and the invention is therefore claimed in any of its forms ormodificationswithin the legitimate and valid scope of the appendedclaims.

Having thus described my invention, I claim:

1. In a. tube cleaner, a rotary carrier, a plurality of planetarycutting elements carried thereby, mounting shafts for said cuttingelements, the axis of said shafts being arranged in inclined relation tothe axis of rotation of the;

carrier, but out of a plane of said axis, polygonal enlargements havingparallel sides eccentrically mounted upon the mounting shafts near oneend, said carrier having radially extending elongated recesses thereinin which the polygonal enlargements of the shafts are seated inpositions selected from several positions of rotative adjustment, saidrecesses being elongated radially with respect to the axis of rotationof the head to permit unrestricted limited radial movement of the shaftsbut not rotative movement thereof and recesses for supporting the endsof theshafts 0pposite said enlargements, means for supporting the otherends of the shafts permittingv a radial movement thereof and means forlimiting the outward movement of the shafts.

2. A rotary tube cleaner having a roughing cutter unit and a finishingcutter unit, each including a plurality of planetary cutter elements andmounting shafts therefor extending in the general direction of the axisof rotation of the cutter unit, one shaft for each cutter element, thecombination including a head for the finishing cutter unit in which theforward ends of the shafts are exposed and a support for the roughingcutter unit, said support including a disclike member abutting said headand provided with bearing seats for supporting the shafts of the cutterelements of the roughing unit and a duo-functional retaining member forinterconnecting the two units, said retaining member securing saiddisc-like member in position and being secured to the head, saidretaining member having a forwardly extending portion to support theforwardly extending portion of the roughing cutter shafts.

3. In a rotary tube cleaner, a head provided with a plurality of pairsof aligned and spaced radially extending slots, a plurality of planetarycleaning elements, means for supporting said cleaning elements in saidhead, said means including a shaft for each cleaning element extendingin the general direction of the axis of rotation of the head, each ofsaid shafts having its ends located in one pair of slots and beingprovided with a rectangular enlargement eccentrically arranged withrespect to the axis of the shaft, each of said enlargements beingarranged to be seated in one of said slots in a non-rotative positionselected from a plurality of positions to thereby obtain a selectedangle of inclination of the axis of the shaft with respect to the axisof rotation of the head but out of the plane of the axis of rotation andmeans engaging the shafts beyond said enlargements for limiting theoutward movement thereof by centrifugal force.

4. In a rotary tube cleaner, a head provided with a plurality of pairsof aligned and spaced radially extending seats having parallel sidesextending radially, a. plurality of planetary cleaning elements, meansfor supporting said cleaning elements in said head, said means includinga shaft for each cleaning element extending in the general direction ofthe axis of rotation of the head, said shaft being provided with apolygonal enlargement having parallel sides, said enlargement beingeccentrically arranged with respect to the axis of the shaft, each ofsaid enlargements being arranged to be non-rotatably seated in one ofsaid seats in a position selected from a plurality of positions tothereby obtain a selected angle of inclination of the axes of the shaftwith respect to the axis of rotation of the head, but out of the planeof the axis of rotation, said seats permitting radial movement of thecutters with respect to the axis of rotation, the shafts end farthestremoved from the enlargement being movably mounted in the other seat ofthe pair including the seat supporting the enlargement and meansengaging the ends of the shafts for limiting the radial movement of saidcutters.

5. A rotary tube cleaner having a roughing cutter unit and a finishingcutter unit, each including a plurality of planetary cutter elements andmounting shafts therefor extending in the general direction of the axisof rotation of the tube cleaner, one shaft for each cutter element, thecombination including a head for the finishing cutter unit in which theforward ends of the shafts are exposed and a support for the roughingcutter unit, said support including a disc-like member abutting saidhead and provided with bearing seats for supporting the ends of theshafts of the cutter elements of the roughing unit and a dual functionalretaining member threadedly engaging the head, said member beingprovided with a collar abutting said disc-like member to clamp saiddisc-like member to the cutter head, and having a forwardly extendingportion to support the forwardly extending ends of the roughing cuttershafts.

6. In a tube cleaner, a rotary carrier, a planetary cutter, a polygonalblock having parallel sides, pivot means for said cutter eccentricallypositioned with respect to the center of the polygon and substantiallynormal to a plane common to the sides thereof, the axis of said pivotmeans being generally parallel to the axis of rotation of the carrier,said carrier having two spaced substantially radially extending guidewalls in which the polygonal block is seated in a' position selectedfrom a plurality of positions of rotative adjustment for centrifugalsliding and means to prevent radial and axial displacement of said blockand cutter.

7. In a tube cleaner, a rotary carrier, a planetary cutter, arectangular block, pivot means for said cutter eccentrically positionedwith respect to the center of the rectangular block and substantiallynormal to a plane common to the sides thereof, the axis of said pivotmeans being generally parallel to the axis of rotation of the carrier,said carrier having a substantially radially extending guide slot inwhich the block is seated in a position selected from a. plurality ofpositions of rotative adjustment for centrifugal sliding and means toprevent radial and axial displacement of said block and cutter.

S. In a tube cleaner, a rotary carrier, a planetary cutter, a polygonalblock having parallel sides and having an integral pivot for said cuttereccentrically positioned with respect to the center of the polygon andsubstantially normal to a plane common to the sides thereof, the axis ofsaid pivot being generally parallel to the axis of rotation of thecarrier, said carrier having a substantially radially extending guideslot in which the polygonal block is seated in a position selected froma plurality of positions of rotative adjustment for centrifugal slidingand means to prevent radial and axial displacement of said block andcutter.

9. A rotary tube cleaner having a roughing cutter unit and a finishingcutter unit, each including a plurality of planetary cutter elements andmounting shafts therefor extending in the general direction of the axisof rotation of the cutter unit, one shaft for each cutter element, thecombination including a head for the finishing cutter unit in which theforward ends of the shafts are supported and a support for the roughingcutter unit, said support including a disclike member abutting said headand provided with bearing seats for supporting the shafts of the cutterelements of the roughing unit and a duo-functional retaining member forinterconnecting the two units, said retaining member axially clampingsaid disc-like member in position and being detachably and rigidlysecured to the forward end of the head, said retaining member having aforwardly extending portion to support the forwardly extending portionof the roughing cutter shafts.

- VIRGIL H. BAKER.

